I use natural population variation to identify the effects of class size and composition on student achievement. I isolate the credibly random component of population variation in each grade and school district and use this component to generate instrumental variables for class size and...

"Using exogenous secondary school assignments to remove self-selection bias to schools and peers, I obtain credible estimates of (1) the effect of attending schools with higher-achieving peers, and (2) the direct effect of peer quality improvements within schools, on the same population. While...